For example, in a single layer type optical disc, such as a DVD-R/RW, a border zone is recorded after information which is already recorded in a user data area. By this, compatibility is maintained between an information reproducing apparatus or reproduce-only equipment (hereinafter merely referred to as a “player etc.”), such as a player and a ROM drive, and an information recording apparatus or information recording/reproducing apparatus (hereinafter merely referred to as a “recorder etc.”), such as a recorder and a RAM drive. The “border zone” herein is an area for buffering i.e., a buffer area to prevent an unrecorded area from adjacently lying immediately after the information already recorded in the user data area or immediately after an area in which the information is recorded, as in a lead-out area in a DVD-ROM or the like. More specifically, the border zone has a structure prepared in order to perform an additional or postscript recording method, such as a multi session in a CD-R, even on a DVD-R. Incidentally, a process of recording the border zone is generally referred to as a “border close (process)”. By recording the border zone so as not to allow, on the DVD-R or the like, the unrecorded area to adjacently lie the information already recorded in the user data area, it is possible to perform normal control of tracking servo, with respect to a DVD-R drive in which a push-pull method is adopted as a tracking method, by using an optical pickup of a DVD-ROM reproduce-only drive in which a phase difference method is adopted. As described above, the presence of the border zone prevents such a situation that the optical pickup of the player etc. jumps out of the already recorded user data area into the unrecorded area which is spread on the outer circumferential side thereof.
On the other hand, in an information recording medium, such as a CD and a DVD, there is developed a multiple layer or multilayer type, or two-layer type (i.e. dual layer type) optical disc, in which a plurality of recording layers are laminated or pasted on the same substrate, as descried in patent documents 1, 2, and the like. On the recorder etc. for recording information onto such a multilayer type optical disc, laser light for recording is focused onto a recording layer located on the front or the closest side (referred to as an “L0 layer”, as occasion demands, in the application), as viewed from a laser light irradiation or emission side, to thereby record the information into the L0 layer in a rewritable method or irreversible change recording method by heat or the like. Then, the laser light is focused onto a recording layer located on the rear or farther side (referred to as an “L1 layer”, as occasion demands, in the application), as viewed from the laser light irradiation side, through the L0 layer and the like, to thereby record the information into the L1 layer in a rewritable method or irreversible change recording method by heat or the like.
In particular, there is also disclosed a technology of performing the recording or reproduction in an “opposite manner” with respect to the L0 layer and the L1 layer. The “opposite manner” herein is a recording or reproducing manner in which the directions of the track passes are opposite between the two recording layers. On the two-layer type optical disc in the opposite manner, as disclosed in a patent document 3, it is necessary to record a middle area as a buffer area on the disc outer circumferential portions of the L0 layer and the L1 layer. The “middle area” plays the same role as the lead-out of the single layer type optical disc, and the above-mentioned border zone. The “middle area” is a buffer area to prevent an unrecorded area from adjacently lying immediately after the user data area in which the information is recorded.
Patent document 1: Japanese Patent Application Laid Open NO. 2000-311346
Patent document 2: Japanese Patent Application Laid Open NO. 2001-23237
Patent document 3: Japanese Patent Application Laid Open NO. 2000-503446
Patent document 4: Japanese Patent Application Laid Open NO. 2002-133667
Patent document 5: Japanese Patent Application Laid Open NO. 2003-59059
Patent document 6: Japanese Patent Application Laid Open NO. Hei 9-16966
Patent document 7: Japanese Patent Application Laid Open NO. 2001-23237